Income taxes - Schedule of Income (Loss) from Continuing Operations Before Provision (Benefit) for Income Taxes (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Taxes Disclosure [Line Items]
U.S.	$ 67,692	$ 16,996	$ 48,405
Non-U.S.	15,036	2,445	1,959
Income (loss) before income taxes	$ 82,728	$ 19,441	$ 50,364